1. Field of the Invention
This invention generally relates to circuit breakers and, more particularly, to an improved drawout and interlock assembly for manually racking a low-voltage circuit breaker of the molded case type into and out of operative relationship with the panelboard of distribution switchboard apparatus.
2. Description of the Prior Art
In certain types of low-voltage distribution switchboard and power assemblies it is frequently necessary to mount the individual circuit breakers within a protective metal enclosure in such a manner that the breakers can be drawn out of engagement with the panelboard for replacement or test purposes and then be returned to its original connected position in a convenient and positive manner. Various kinds of drawout mechanisms have been developed and used in the prior art for this purpose and are disclosed in the following U.S. Pat. Nos.: 2,273,002 (Mahoney); 2,544,314 (Hebbel, Jr.); 2,678,976 (Caswell); 2,777,024 (West); 3,343,042 (Cellerini et al.) and 4,012,610 (Ericson et al.).
While the prior art drawout assemblies were satisfactory from a functional standpoint and, in some embodiments, were provided with an interlock arrangement for tripping the circuit breaker at predetermined times during the drawout operation, they were complicated and required a large number of parts which made them difficult and expensive to manufacture. The coaction required between the various components of the prior art drawout and interlock assemblies to provide the smooth reciprocal movement of the breaker necessitated the use of skilled maintenance men to maintain the apparatus in working condition. This further increased the cost of ensuring that the equipment operated in a positive reliable manner over long periods of time in different environments.
The foregoing problems and disadvantages associated with the prior art structures are avoided in accordance with the present invention by providing a drawout and interlock assembly which permits a low-voltage circuit breaker to be manually racked into connected and disconnected-test positions relative to the panelboard of the distribution switchboard apparatus in a very positive and efficient manner with a minimum of parts. These objectives are achieved by mounting a laterally-extending coupler structure to the back of the circuit breaker and securing a laterally-extending receptor structure to the stationary plug-in power components of the panelboard in such a position that the receptor structure slidingly receives and engages the coupler structure in telescopic fashion during the drawout and draw-in operations. The receptor structure includes a drive mechanism that is rotated by an operating handle and pivotally engages slotted portions of the coupler structure in cam-like fashion such that the circuit breaker is reciprocally moved toward and away from the power plug-in components when the handle is actuated. A spring-biased interlock lever is operated in toggle-like fashion by an actuating arm that comprises part of the drive means and cooperates with the interlock lever in such a manner during the drawout and draw-in operations that the interlock lever automatically depresses an interlock button on the back of the circuit breaker which permits the breaker to operate in the normal manner when the breaker has been racked into its disconnected-test position by the drawout assembly.
A pair of secondary plug-in connector components are mounted on the receptor and coupler structures in such a way that they are automatically compressed into mating engagement during the initial draw-in operation and then remain connected as long as the circuit breaker is held in operative relationship with the panel switchboard by the drawout mechanism. These secondary conductor components permit the control and test circuit components of the breaker to be tested when the circuit breaker is in its drawout position and disconnected from the power plug-in terminals of the panelboard.
The construction and structural organization of the various parts of the interlock mechanism and coupler and receptor structures of the drawout assembly are such that the desired manual racking of the circuit breaker into and out of the panelboard of the distribution switchboard apparatus is accomplished in a very positive and reliable manner with parts that are rugged and readily manufactured and assembled and whose number is a minimum.